FXC-4570 feat(rf): Added symmetric_pseudo option for s_param_def

[dmarek-flex]

Greptile Summary

This PR adds a new symmetric_pseudo option for s_param_def in TerminalComponentModeler, which provides an alternative S-parameter formulation equivalent to the "traveling wave" definition in scikit-rf. The implementation applies a different scaling factor (F = sqrt(1/(2*Z))) that ensures the resulting S-matrix is symmetric when port impedances differ.

Key changes:

• Extended SParamDef type to include symmetric_pseudo as a valid literal value
• Modified compute_F() to handle the new symmetric_pseudo scaling with proper mathematical documentation
• Updated terminal_construct_smatrix() to route symmetric_pseudo requests to pseudo wave matrices (reusing existing infrastructure)
• Added comprehensive error handling with consistent error messages across all modified functions
• Extended s_to_z() conversion logic to properly handle symmetric_pseudo (treating it like pseudo for conjugate handling)
• Added test coverage validating symmetric_pseudo against scikit-rf's "traveling" wave definition

Issues found:

• Test file contains debugging print() statements that should be removed
• Some test assertions are commented out and need to be either removed or uncommented and fixed

Confidence Score: 4/5

• This PR is safe to merge after removing debugging code
• The implementation is mathematically sound and follows established patterns in the codebase. Error handling is consistent and comprehensive. The only issues are temporary debugging artifacts (print statements and commented-out tests) that should be cleaned up before merge.
• tests/test_plugins/smatrix/test_terminal_component_modeler.py needs cleanup of debugging code

Important Files Changed

Filename	Overview
tidy3d/plugins/smatrix/utils.py	implemented symmetric_pseudo scaling in compute_F() with proper documentation and error handling
tidy3d/plugins/smatrix/analysis/terminal.py	added symmetric_pseudo case to terminal_construct_smatrix() with proper error handling
tests/test_plugins/smatrix/test_terminal_component_modeler.py	added tests for symmetric_pseudo but contains debugging print statements and commented-out assertions that need cleanup

Sequence Diagram

sequenceDiagram
    participant User
    participant ModelerData as TerminalComponentModelerData
    participant Constructor as terminal_construct_smatrix
    participant Utils as utils.compute_F
    participant S2Z as utils.s_to_z

    User->>ModelerData: smatrix(s_param_def="symmetric_pseudo")
    ModelerData->>Constructor: terminal_construct_smatrix(s_param_def="symmetric_pseudo")
    
    alt symmetric_pseudo
        Constructor->>ModelerData: get port_pseudo_wave_matrices
        Note over Constructor: Reuses pseudo wave matrices<br/>with different scaling
    else power
        Constructor->>ModelerData: get port_power_wave_matrices
    else pseudo
        Constructor->>ModelerData: get port_pseudo_wave_matrices
    end
    
    ModelerData-->>Constructor: a_matrix, b_matrix
    Constructor->>Constructor: compute S = b @ inv(a)
    Constructor-->>ModelerData: S-matrix
    ModelerData-->>User: MicrowaveSMatrixData
    
    opt Convert to Z-matrix
        User->>ModelerData: s_to_z(s_param_def="symmetric_pseudo")
        ModelerData->>S2Z: s_to_z(S, reference, s_param_def)
        S2Z->>Utils: compute_F(Z, "symmetric_pseudo")
        Utils-->>S2Z: F = sqrt(1/(2*Z))
        Note over S2Z: Uses non-conjugate Zport<br/>(same as pseudo)
        S2Z->>S2Z: Z = solve(I - F^-1*S*F, ...)
        S2Z-->>ModelerData: Z-matrix
        ModelerData-->>User: Impedance matrix
    end

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Diff Coverage

Diff: origin/develop...HEAD, staged and unstaged changes

• tidy3d/plugins/smatrix/analysis/terminal.py (100%)
• tidy3d/plugins/smatrix/data/terminal.py (100%)
• tidy3d/plugins/smatrix/types.py (100%)
• tidy3d/plugins/smatrix/utils.py (100%)

Summary

• Total: 13 lines
• Missing: 0 lines
• Coverage: 100%

[dmarek-flex]

@weiliangjin2021 @yuanshen-flexcompute Still can be modified if you want but I enabled this symmetric version of pseudo waves and tried to put all the relevant info in one place. I have another issue to track the docs PR for summarizing the various S parameter amplitude definitions and their properties.

[weiliangjin2021]

looks good to me, except that it should be named as symmetric_pseudo